1. Field of the Invention
The present invention relates to backlight modules, particularly, to an edge-lighting type backlight module for use in, for example, a liquid crystal display (LCD), and methods for making the backlight modules.
2. Discussion of the Related Art
In a liquid crystal display device, a liquid crystal is a substance that does not itself radiate light. Instead, the liquid crystal relies on light received from a light source, thereby displaying data images. In the case of a typical liquid crystal display device, a backlight module powered by electricity supplies the needed light. Generally, backlight modules can be classified into an edge lighting type or a bottom lighting type based upon the location of lamps within the device.
Referring to FIG. 6, a typical edge lighting type backlight module 10 includes a frame 11, a light reflective plate 12, a plurality of light emitting diodes 13, a light guide plate 14 and at least one optical plate 15. The frame 11 includes four sidewalls 114 that connect with each other to form a receiving space 112. The light reflective plate 12, the light guide plate 14 and the optical plate 15 are stacked in that order, and are mounted in the receiving space 112 together. The light guide plate 14 includes a light input surface 141, and a light output surface 142 adjoining the light input surface 141. An inner side surface of the sidewalls 114 facing the light input surface 141 defines a plurality of grooves 111 therein. The light emitting diodes 13 are received in the corresponding grooves 111 of the sidewall 114.
Referring to FIG. 7, each light emitting diode 13 includes a base 131, a semiconductor chip 132 fixed on the base 131, and a transparent resin member 133 sealed with the semiconductor chip 132 at one side of the base 131. Also referring to FIG. 6, the light guide plate 14 includes a light input surface 141, and a light output surface 142 adjoining the light input surface 141. The transparent resin member 133 of each of the light emitting diodes 13 faces the light input surface 141. In use, light from the light emitting diodes 13 passes through the light input surface 141 and enters the light guide plate 14. The light is reflected and refracted in the light guide plate 14, and finally surface light is outputted from the light output surface 142.
Generally, it is difficult to assemble the light emitting diodes 13 to be in continuous contact with the light input surface 141 of the light guide plate 14. A space still exists between the light input surface 141 and the transparent resin members 133 of the light emitting diodes 13. Because a refractive index of the transparent resin members 133 of the light emitting diodes 13 is relatively larger than of the refractive index of air, when light from the semiconductor chip 132 passes through the space, the light undergoes total reflection at the space. As a result, the light energy utilization ratio of the backlight module 10 is reduced.
What is needed, therefore, is a backlight module that overcomes the above mentioned disadvantages. Methods for making the backlight module are also desired.